The present invention relates to a rewritable storage medium, a recording apparatus and a playback apparatus for use with the storage medium, a method for recording data on the storage medium, and to a computer program executing the recording method. More particularly, the present invention is adaptive to, and preferably used with, an optical disc on which a large amount of still picture data is recorded.
Large-capacity, rewritable optical disc recording media, such as DVD-RAMs or DVD-RWs, have been made available, and many technologies for recording picture data or audio data on the media are now being developed. Video data coded, for example, in the MPEG (Moving Picture Experts Group) system described in the ISO/IEC11172 or ISO/IEC13818 standard is usually used. Still picture data coded in the intraframe compression method (I picture) of the MPEG (Moving Picture Experts Group) system or in the JPEG system described in the ISO/IEC10918-1 standard is usually used.
Digital VCRs(digital video cassette recorders) using magnetic tapes as recording media or electric still cameras using memories such as a flash memory as recording media are already in practical use for storing coded video or still pictures with audio.
Recording apparatuses using optical discs as recording media, such as DVD-RAMs, have many advantages over conventional digital VCRs or electric still cameras in that they feature random accessibility which cannot be attained by magnetic tapes, large-capacity which cannot be achieved by memories such as a flash memory, and a low cost per bit. Therefore, recording apparatuses using optical disc media allow the user to play back data independently of the sequence in which data was recorded and to process as many as tens of thousands of still pictures. For this reason, optical disc recording media are expected to be widely used as new AV (audio-visual) recording media.
A DVD-RAM disc allows moving pictures and still pictures to be mixed. Especially, for still pictures, a huge number of still pictures which cannot be recorded by a conventional electric still camera can be recorded. For example, a 4.7 GB DVD-RAM disc can record thereon about 64,000 still pictures each of which is an MPEG-coded still picture (I picture) of about 80 KB.
Unlike a storage medium such as a digital VCR tape from which data is played back in the order in which it was recorded, an optical disc medium such as a DVD-RAM disc allows the user to access data randomly. For data to be accessed randomly, management information, such as the addresses and sizes of still picture data as well as the playback times of audio data recorded with still pictures are recorded.
Playing back still pictures with a playback apparatus requires two steps. First, a still picture data address and so on are read from the management data recorded on the optical disk medium, and then still picture data recorded at the address that was read is played back. Therefore, when playing back a plurality of still pictures, each still picture requires the above two steps.
Also, recording still pictures and so forth onto an optical disc with a recording apparatus requires two steps. First, still picture data is recorded, and then management information such as the still picture data address is recorded. Therefore, when recording a plurality of still pictures, each still picture requires the above two steps.
The optical disc recording or playback apparatus has an optical head for recording and playing back information. This optical head is slow in accessing data because it is larger and heavier than a magnetic head. Therefore, playing back or recording a plurality of still pictures, which requires two steps, takes long and the apparatus cannot perform random access quickly.
To solve this problem, the optical disc recording apparatus and the playback apparatus store management information, read from the optical disc, into memory. Once the management information is stored into memory of the playback apparatus, the apparatus need not read management information from the disc each time it plays back a still picture, thus reducing the time needed to playback a plurality of still pictures. Also, the recording apparatus stores management information about a plurality of still pictures into the memory of the apparatus and records the management information onto the disc at a time. This eliminates the need to record management information each time a still picture is recorded, thus reducing the time needed to record a plurality of still pictures.
However, because a large-capacity storage medium such as a DVD-RAM records tens of thousands of still pictures thereon, the amount of management information on recorded still pictures becomes very large and a large amount of memory capacity is needed in the apparatus. Although the memory price has gone down recently, it is difficult to install megabytes of memory onto an AV apparatus. In addition, considering the memory backup provided for use at emergency, it is unrealistic for an AV apparatus to process megabytes of management information.
To solve this problem, a technology is disclosed in the specification of the European Patent Application No. 99304691.1 filed on Jun. 16, 1999 or the corresponding U.S. patent application Ser. No. 09/332,882 filed on Jun. 15, 1999 by some of the inventors of the present invention. To prevent an increase in the management information size, the technology disclosed in the above patent application records management information, such as data addresses and sizes or audio data playback times, in variable-size management information tables proportional in size to the number of still pictures or the number of audio data pieces.
However, the technology described above does not take the following into account. First, the technology does not support the function to manage still picture data recording times. Because the technology described above does not support a search for data with the use of recording times, there is a problem with processing a request to search a huge number of still pictures for a desired still picture.
For example, as shown in FIG. 3, when a recording time (RECTM) is represented by a 7-byte data structure composed of the year (2 bytes), month (1 byte), day (1 byte), hour (1 byte), minute (1 byte), and second (1 byte), adding the recording time (RECTM) to each of about 64,000 still pictures requires that the data size of the management information used by the above-described technology be increased by as many as about 438K bytes (=64,000xc3x977).
As mentioned above, the system controller within the apparatus should have the management information always in its own memory for quick random access. To reduce the memory size (cost reduction) of AV apparatuses, that is, to reduce the cost, the data size of the management information must be minimized.
It is a first object of the present invention to provide a recording apparatus and a playback apparatus, primarily used for optical discs, which allow the user to search for data based on recording times and which have a data structure preventing the data size of management information from increasing, and computer programs which control these apparatuses.
Second, the technology does not support the function to solve problems associated with still picture deletion.
FIG. 12 shows the still picture management method according to the technology described above. First, still picture group management information (VOBGI) 103 is provided to manage a plurality of still picture data pieces (VOB) 101 as a still picture group (VOBG) 102. The still picture group management information (VOBGI) 103 comprises still picture group identification information (VOBG_ID) 104, start and end address information (VOBG_Address) 105 on the still picture group (VOBG) 102, number-of-pictures information (V_I_Number) 1015 representing the number of still pictures managed in this group, picture management information table (V_I_Table) 1016 containing only picture management information (V_I) 1017 on the pictures of the still picture data (VOB) 101, number-of-audio-data information (A_I_Number) 1018 representing the number of audio data pieces managed in this group, and audio management information table (A_I_Table) 1019 containing only audio management information (A_I) 1020 on the audio data. The picture management information (V_I) 1017 comprises an picture data size (V_Size) 1021 and audio pointer information (A_I_PTR) 1022 providing a link to the audio management information (A_I) 1020 corresponding to the audio data to be played back in synchronization with the picture. The audio management information (A_I) 1020 comprises audio data address information (A_Address) 1023, audio data size (A_Size) 1024, audio playback time (A_PTM) 1025, and audio pointer information (A_I_PTR) 1026 providing a link to other management information (A_I) 1020. When there is no audio data to be linked, NULL is recorded in the audio pointer information (A_I_PTR) 1022, 1026 to indicate an invalid value.
The technology described above has two separate tables: picture management information table (V_I_Table) 1016 and audio management information table (A_I_Table) 1019. In addition, the audio management information (A_I) 1020 contains audio data address information (A_Address) 1023.
Still picture data and audio data are recorded in files on the storage medium. Because the addresses in the file are contiguous, deleting a still picture and the audio data synchronizing with it causes the file to be restructured to close up the deleted part and to make the addresses contiguous within the file. Therefore, when the recording position of audio data is managed by the audio data address information (A_Address) 1023 within the file, all the audio data address information (A_Address) 1023 after the deleted part must be replaced with new address information generated after restructuring. This will require a very long time for replacing address information when tens of thousands of still picture data are recorded.
Another way to get address information is to simply delete the address information 1023 from the management information shown in FIG. 12 and then to add up the picture and audio data sizes 1021, 1024 beginning with the start, as shown in FIG. 13, (a).
Although this method eliminates the need for address replacement after restructuring described above, following problem arises.
For example, assume that two different data structures described below occur in the file. One data structure, shown in FIG. 13, (b), is composed of the video part (V_Part #1) 1027 of still picture #1, followed by the post-recorded audio part (A_Part #1) 1028 of still picture #1, followed by the video part (V_Part #2) 1029 of still picture #2. Another data structure, shown in FIG. 13, (c), is composed of the video part (V_Part #1) 1030 of still picture #1, followed by the video part (V_Part #2) 1031 of still picture #2, followed by the post-recorded audio part (A_Part #1) 1032 of still picture #1. Although the data structures differ, management information table entries are created as shown in FIG. 13, (a). That is, V_I #1(1017-1) in the picture management information table (V_I_Table) 1016 comprises the picture data size (V_Size #1) 1021-1 of V_Part #1(1027) or V_Part #1(1030) and the audio pointer information (A_I_PTR) 1022-1 providing a pointer to A_Part #1(1028) or A_Part #1(1032). V_I #2(1017-2) comprises the picture data size (V_Size #2) 1021-2 of V_Part #2(1029) or V_Part #2(1031) and audio pointer information (NULL) 1022-2 indicating that there is no audio data to be linked. A_I #1(1020) comprises the audio data size (A_Size #1) 1024 of A_Part #1(1028) or A_Part #1(1032), audio playback time (A_PTM #1) 1025, and audio pointer information (NULL) 1026 indicating that there is no audio data to be linked. Therefore, these two cannot be distinguished.
In addition, the configurations of the picture management information (V_I)(1017) and the audio management information (A_I)(1020) shown in FIG. 12 are redundant. The data sizes may further be reduced.
It is a second object of the present invention to provide a recording apparatus and a playback apparatus for use with an optical disc with a data management structure capable of managing still picture data and audio data to be played back in synchronization the still picture data without any problem, significantly reducing the time needed to re-configure the management information when still pictures are deleted, and reducing the management information sizes.